Centrifugal particle separator



y 22, 1952 K. o. L. SILVERSTOLPE 2,604,261

CENTRIFUGAL PARTICLE SEPARATOR Filed May 28, 1949 mm 3 2 M m A w E Z M M 0 m K JTTORNEY H ab N Patented July 22, 1952 2,604,261 I jCENTRjIFUGAL PARTICLE SEPARATOR Karl Oskar Lennart Silverstolpc,

Stockholm, Sweden Application May 28, 1949, Serial No. 95813 e In Sweden June 15, 1948 zioiaims. (01. 233-26) This invention relates to centrifugal particle separators for separating particles suspended in a liquid contained in'a receptacle, particularly to particle separators for separating particles such as salts, cells, bacteriae and the like suspended in test liquids as are frequently used inconnection with medical tests.

Centrifugal particle separators of the general type, above referred to, as hitherto known generally comprise a vertical shaft arranged to be rotated by an electric motor, preferably with variable speed, and supporting a horizontally mounted disc usually having a number of arms in form of a cross or otherwise suitably shaped. These disc arms serve to support an even number of holders which are movably secured to the disc and serve to receive one or more test-tubes in which the liquids to be tested are contained. As will be apparent, the holders and with them the tubes will swing in a radial direction when the disc is rotated during the centrifugalizing operation.

Conventional centrifugal separators of this type have the disadvantage that the resultants of the centrifugal forces acting upon the liquid are not directed substantially in the direction of the longitudinal-axes of the liquid containing tubes during the entire centrifug-alizing process but will assume various angles relative to these longitudinal axes. As will be apparent, the rotational speed of the disc and, hence, also of the tubes will increase during each centrifugalizing operation from zero speed to full speed in the acceleration period and decrease from full speed to zero speed in the retardationperiod. As a result, all the particles contained in the liquid will not be deposited on the bottom or bottom closure of the tubes but a certainfraction of the particles will be deposited on the side of the tubes or bunched on the lower section of the tubes. Furthermore, during the retardation period the angular position of the aforementioned resultant will generally change, thereby agitating the liquid causing previouslydeposited particles to become unsettled again.

It has already been suggested to mount the tube holders at an angle relative to the supporting disc'so that the mouths of the tubes will face forwardly in the direction of the rotation. However, such an arrangement merely accomplishes that the tubes occupy a'suitable angular position during the acceleration period of thecentrifugalizing operation but not during the full speed period in which the actualcentr-ifugalizing process takes place'and also not during the retardation period. Hence, the difficulties caused by an agitation of the liquid remain.

For-many tests used in modern science an accurate determination of the number of particles suspended in a given volume of liquid is of great importance, for instance in connection with the determination of the urine sediment, etc. Hence, a device permitting an accurate determination of the actual number of particles per unit of liquid is highly desirable.

One of the objects of the present invention is to provide a novel and improved centrifugal particle separator of the general type, above referred to, which permits an accurate and simple determination of the number of particles suspended in a given volume of a test liquid.

Another object of the invention is to provide a novel and improved separator of the general type, above referred to, in which the holders for the said test-tubes are so mounted that the holders and with them the test-tubes can adjust themselves freely at each moment substantially in the direction of the resultants of the forces'acting upon the tubes irrespectively whether the rotational speed of the separator is high or low.

Another object of the invention is to' provide a novel and improved separator of the general type, above referred to, in which the tube holders are so mounted that the tubes, during a period of rapid acceleration, will swing in a direction opposite to the direction of rotation. As a result, the strain on the tubes, usually made of glass, is considerably reduced so that breakage which frequently occurs at the beginning of the operation with conventional separators is practically eliminated with a separator according to the invention.

Other and further objects, features and advantages of the invention will be pointed out hereinafter and set forth in the appended claims forming part of the application.

In the accompanying drawings several embodiments of the invention are shown by way of illustration and not by Way .of limitation.

In the drawings:

Fig. l is a fragmentary plan view of a centrifugal particle separator according to the invention.

Fig. 2 is a modification of the plan view according to Fig. 1.

Fig. 3 is another modificationof the plan view according to Fig. 1.

Fig. 4 is a sectional view of Fig. 1 taken along line IV-IV of Fig. 1.

Fig. 5 is a fragmentary sectional side view of still another modification of a centrifugal particle separator according to the invention, and

Fig. 6 is a plan view of Fig. 5.

Referring first to Figs. 1 and 4 in detail, the centrifugal particle separator according to the invention comprises a vertically mounted drive shaft I arranged to be rotated by a suitable drive means such as anelectric motor (not shown), preferably with variable speed; Shaft I supports a horizontally disposed bracket 3 mounted for rotation in unison with shaft I. Bracket 3 is shown as a disc having four arms positioned in cross-shape. However, any other suitable shape of the disc or a disc having more or less than four arms can also be employed. Generally, an even number of arms symmetrically arranged is advisable. While only one complete arm is illustrated, it should be assumed that all the arms are substantially identically shaped. The end of each arm supports a holder 2 shown as a substantially cylindrically shaped tube open-at the top and closed at the bottom.

Tube 2 may either receive the test liquid directly or one or more conventional test-tubes I8 containing the liquid and cushioned by a soft pad I9.

Generally, it is advisable to provide an identical holder at the end of each arm to avoid an unbalance of the system while spinning. However, in certain instances it is also possible and practical to employ differently designed holders, an uneven number of holders or only one holder in which case it may be necessary to balance the system by suitable counterweights,

Holder 2 is supported on its arm by means of a universal joint, more specifically by a so-called gimbals suspension. This suspension is shown as comprising an inner gimbal ring 4 and an outer gimbal ring 5 concentrically mounted with the inner ring. Ring 4 receives holder 2 and is pivoted to ring 5 by two diametrically oppositely arranged pivots 6 and I. Similarly, ring 5 is pivoted by two diametrically oppositely arranged pivots 8 and 9 to bracket 3 which is bi-furcated at the end of each arm. As a result, ring 5 can freely pivot relative to the bracket. According to Figs. 1 and 4, the pivots 6, 1 and 8, 9 are so positioned that the center lines thereof cross each other at a right angle, the center line of pivots 6, I being positioned on a radial line extending from the axis of drive shaft I. While such an arrangement of the pivots has been found to be generally advantageous, other angular dispositions are also practical in certain instances.

According to Fig. 2, the disposition of the pivots is reversed in comparison with Figs. 1 and 4, that is, the outer pivots 8 and 9 are aligned with the aforementioned radial line.

According to Fig. 3 both pairs of pivots form an angle of less than 90, for instance of 45 with the radial line.

In the last-mentioned case it is advantageous to arrange the two pivot pairs in such manner that the two center lines thereof form the same angle with the connecting line between the common center axis or point of the rings and the center axis of drive shaft I. Hence, the center line of pivots 6 and I may be varied between 0 and 90 relative to the aforesaid connecting line while the center line of pivots 8 and 9 may be varied correspondingly between 90 and 0 relative to the said connecting line.

As will now be apparent, each of the gimbals suspension systems, hereinbefore described, swings about a suspension center defined by the intersection of the pivot axes of the two gimbals rings.

During centrifugation at full speed, it is desirable that the holders 2 with the test-tubes occupy substantially horizontal positions. As will be noted, such position can be attained with the arrangements according to Figs. 1, 3 and 4 while the arrangement according toFigiZ, does not permit a horizontal position of the holders, the extension 3 of bracket 3 being in the way.

To prevent the holders from swinging outwardly beyond a horizontal position, it is advisable in many instances to provide stop means limiting the swinging movements of the holders within the vertical plane through the center axis A-A of shaft I and the line BB which represents the center axis of a holder when the same is in its starting or rest position. Such stop means may be mounted on the holders proper or the holder suspension and engage the bracket when the holders reach the maximal position or they may be mounted on the bracket or any suitable part of the separator in which case the stop means engage theholders or the holder suspension means in the maximal position thereof. The stop means may comprise dogs, studs, pins, arms, shoulders, etc. According to the illustrated embodiment the ring which controls the pivotal movement of the holders in planes through the axis of the drive shaftin Figs. 1 and 4 the ring 5--is provided with a stud III which abuts against bracket 3 when the holders are in a horizontal position.

A similar stop I I secured to ring 5 prevents the holder to swing inwardly beyond its starting or rest position, generally a downwardly directed vertical one. It is of course also possible to secure the second stop II to the bracket, in which case it will engage ring 5 in the position shown in Fig. 4.

The ring 4 or 5 which permits the respective holder to occupy a position in which the axis of the holder forms an angle with the vertical plane through the center line AA of' the drive shaft and the center line BB of the holder is also preferably provided with stop means, such as stops I2 and I3 in form of studs, pins or the like, which prevent the last mentioned angle from increasing beyond a selected degree, for instance 30 to 45, in either direction, thereby limiting the lateral pivotal movements of the holders in either direction during the acceleration and retardation periods.

Furthermore, it is often advantageous to fit the pivots of the rings permitting the lateral movements of the holders rather tightly in the respective bearings so that the lateral movements of the holders are comparatively slow,

According to the embodiment shown in Figs. 5 and 6, each holder is supported by means of a universal joint in form of a socket and ball bearing. The illustrated bearing comprises a socket or cage I5 mounted on or integral with the respective arm of disc 3. Socket I5 houses a ball I4 the center bore of which receives the holder proper. As will be noted, both the socket and the bore are flattened at top and bottom. To increase the possible angular movements of the holders, socket or cage I5 is provided with small recesses I6 at both sides. However, in spite of these recesses the holder movements in different directions are still limited. In case it is desirable to permit the holders to occupy a substan tially horizontal position, the socket can be provided with a circumferential gap or recess IT in the side of the socket facing away from the. drive shaft. The circumferential width-of this gap is preferably so selected that the holders can perform all the pivotal movements thatsarewdesir able during the entire :centri-fugalizing operation. Of course, it will beev-ident that the width-of the gap 'must be so selected that suiilcient bearing strength is retained to withstand'the forces acting upon the-joint it, it; In practice, the posslbleangle of the gap relative to the horizontal connecting line betweentheshaft :axis and the holder axis is controlled by the relation between the diameter of holder a and the diameter of socket is and is generallybetween l and 30 in either direction from said line.

It has been found advantageous to fitthe ball rat-her tightly in'its socket sothat the holder movements in different directions are not too fast during the difierent'phases of the operation. a The suspension center of the, ball and socket system according to Figs. and -6 is concentric with the center of ball 54. I

By using detachable inserts of conventional design, several tubes, usually two to three, can be treated simultaneously in each holder.-

Whether one or more tubes are inserted in each holder, it is evident that uniform holders, suspension means for the same,;sirn-ilar inserts, and an equal number of test-tubes with equal quantities of liquid in them should be employed in symmetrical arrangement to balance the separator While spinning, as has been previously mentioned. Also, the various holders, inserts, tubes etc. mounted on-the disc should have an approximately equal weight.

It has further been found advantageous to a make the mass of the suspension means proper as small as possible while the holdersthe'mselves should have a comparatively large mass and hence be comparatively heavy. This has the advantage that during the retardationperiod each holder including one or more test-tubes will occopy a forwardly directed slanted position (for instance of a few degrees).- Such slanting position attributes to a preventionof unsettling the liquid during the retardation period.

Finally, it should bementioned that the center of ring 4 does not have necessarily to coincide with the center of ring 5, but the ring 4 may be disposed at different level along the center :axis

of the respective holder, for instance when one ring or both rings are mounted in a stirrup-like fashion.

While the invention has beendescribed in detail with respect to certain now preferred examples and embodiments of theinvention it will be understood by those skilled in the art after understanding the invention, that various changes and modifications may be made without departing from the spirit and scope of the invention and it is intended therefore, "to cover all such changes and modifications in the ap pended claims.

What is claimed as new and desired to be secured by Letters Patent'is: V

1. In a centrifugal testing separator for separating particles suspended in a liquid test sample contained in a receptaclathe combination of a vertically mounted drivingishaft, a bracket substantially horizontally extending from said shaft and mounted for rotation in unison therewith, a holder adapted to receive a liquid containing Ireceptacle, and .universal joint suspension .means supporting the holder on the bracket freely swingable relative to the bracket in the directionof the respective resultant of I the centrifugal .and inertia forces andother forces acting upon the holder and varying corresponding to the changes in the rotational speed of the driving shaft during the cause of acentrifugalizing operation.

2. In a centrifugal 'testingxseparator for. separating particles suspended in atest sample liquid' contained ina receptacle, the combination of a vertically mounted driving shaft, a bracket substantially horizontally extending from said shaft and mounted for rotation in unison therewith, :an even number of holders each adapted to receive aliquid containing receptacle, and a corresponding number of substantially uniformly spaced universal .jolnt'means supporting the respective holder freely swingablerelative to the bracket, .ieach holder support means being positioned on the bracket diametrically opposite to another holder support'means.

3. .A centrifugal'te'sting separator as described in claim '2, wherein the massof a'holder is substantially in excess. of the mass of'the respective holder support means, the mass of the support means being held as small as practical.

4. In a centrifugal testing separator for sep- 'aratingparticles suspended in a'liquid test sample contained in a'receptac'la'the combination of a vertically'mounted driving shaft, a bracket substantially horizontally extending from said shaft and mounted for rotation in unison'therewith, an even number of holders each adapted to receive a liquid containing receptacle, and a corresponding number of substantially uniformly spaced gimbals suspension means supporting the hold ers on the bracket, each of said suspension means being positioned on the bracket diametrically opposite to another one of said suspension means.

'5. A'testing separator as described in claim i, wherein each of said gimbals suspension means comprises an inner and an outer gimbal ring, a pair of diametrically oppositely positioned pivots pivoting the inner ring to the outer ring, and a second pair of diametrically oppositely positioned ivots pivoting the outer ring to the bracket, the center line through'thepivots of the inner ring being positioned at an angle variable between 0to relative to the horizontal connecting line between the axis of the driving shaft and the common axis through the centers of the said rings, and the center line through the pivots of the said outer gimbal ring being positioned at an angle of 90 thereto.

6. A testing separator as described in claim 4, wherein each of said gimbals suspension means comprises an inner and an outer gimbal ring, a pair of diametrically oppositely positioned pivots pivoting'the inner ring to the outer ring, and a second pair of diametrically oppositely positioned pivots pivoting theouterring to the bracket, said inner pivots being positioned in alignment on the same radial line extending from the axis of said shaft, and said outer pivots being positioned on different radii extending from the shaft axis and at the same radial distance from the said shaft axis.

7. A testing separator as described in claim .4, wherein each of said gimbals suspension means comprises an inner and an outer gimbal ring, a pair of diametrically oppositely positioned pivots pivoting the inner ring to the outer ring, and a second pair of diametrically oppositely positioned pivots pivoting the outer ring to the bracket, saidinner pivots being positioned on dif-- ferent radii extending from the shaft axis and at the same radial distance from the said axis, and

said outer pivots being positioned in alignment on the same radial line extending from said shaft axis and at equal distance from the common center axis of said rings.

8. A testing separator as described in claim 2, in combination with stop means limiting the universal swinging movements of said holders in response to thecentrifugal and inertiaforces and other forces acting upon the same;

9. A testing separator as described in claim 4, in combination'with stop means-for each of'the holder suspension means and coacting with the said bracket for limiting outwardly swinging movements of the holders in the vertical plane through the axis of said driving shaft and the axis of the respective holder when the bracket and the holders are in the position of rest, each of the said stop means being arranged and positioned to be in stopping engagement with said bracket upon the respective holderoccupying a position in which the center axis of the holder is substantially at a right angle to the axis of the driving shaft.

10. A testing separator as described in claim 4, in combination with stop means for each of the holder suspension means and coacting with the said bracket for limiting inwardly swinging movements of the holders in the vertical plane through the axis of said driving shaft and the axis of the respective holder when the bracket and with it the holders are in the position of rest, each of the said stoppng means being arranged and positioned to be in stopping engagement with said bracket upon the respective holder occupying a position in which the center axis of the holder is substantially parallel to the axis ofthe driving shaft.

11. A testing separator as described in claim 4, in combination with stop means for each of the holder suspension means and coacting with said outer ring for limiting lateral swinging movements of the holders relative to a vertical plane through the axis of said shaft and the axis of the respective holder, each of said stop means being arranged and positioned to be in stopping engagement with said outer ring upon the respective holder occupying a position at an angle of 45 at the utmost relative to said plane.

12. In a centrifugal testing separator for separating particles suspended in a liquid test sample contained in a receptacle, the combination of a vertically mounted driving shaft, a bracket substantially horizontally extending from said shaft and mounted for rotation in unison therewith, an even number of holders each adapted to receive a liquid containing receptacle, and a corresponding number of substantially uniformly spaced universal joint support means in form of ball and socket suspension means supporting the holders on the bracket, each of said support means supporting the respective holder freely swingably in the direction of the respective resultant of the centrifugal and inertia forces and other forces acting upon the holder and varying corresponding to the changes in the rotational speed of the driving shaft during the course of a centrifugalizing operation.

13. A testing separator as described in claim 12, wherein each of said suspension means comprises a socket member on said bracket and a ball member secured to the respective holder and pivotally fitted in the socket.

14. A testing separator as described in claim 13, wherein the top and bottom of each of said socket members are flattened, each of said socket members including recesses in its flattened top and bottom for increasing the range of pivotal movements of the respective supported holder.

15. A testing separator as described in claim 12, wherein each of said suspension means comprises a socket member on said bracket and a ball member secured to the respective holder and pivotally fitted in the socket, the top and bottom of each socket member being flattened, each of said socket members including a circumferential recess in its side facing away from said shaft, the circumferential width of said recess beng selected to provide for an outward pivotal movement of a holder up to an angle of relative to the axis of said shaft and for a pivotal movement of the holders within a selected angular range in the direction of the rotational path of the holders.

16. A testing separator as described in claim 1, wherein said holder comprises a substantially cylindrically shaped tube closed at its bottom and arranged to receive at least one test-tube.

17. In a centrifugal testing separator for separating particles suspended in a liquid test sample contained in a receptacle, the combination of a vertically mounted driving shaft, a bracket substantially horizontally extending from said shaft and mounted for rotation in unison therewith, an even number of holders each adapted to'receive at least one liquid containing receptacle, and a corresponding number of substantially uniformly spaced universal joint suspension means each supporting one of said holders on the bracket, each suspension means including coacting components for supporting the respective holder freely swingable relative to the bracket, one of said coacting components being on the bracket and another on the respective holder, each holder suspension means being positioned on the bracket diametrically opposite to another holder suspension means.

18. In a centrifugal testing separator for separating particles suspended in a liquid test sample contained in a receptacle, the combination of a vertically mounted driving shaft, a bracket substantially horizontally extending from said shaft and mounted for rotation in unison therewith, a holder adapted to receive at least one liquid containing receptacle, and universal joint support means supporting the holder on the bracket, said support means including joint members for universal movements of the holder relative to the bracket, said joint members including an outer joint member mounted on the bracket and an inner joint member mounted on the holder, said outer joint member being held captive within the bracket freely swingable relative to the bracket, and said inner joint member being held captive within said outer joint member freely swingable relative to the outer joint member in the direction of the respective resultant of the centrifugal and inertia forces and other forces acting upon the holder and varying corresponding to the changes in the rotational speed of the driving shaft during the course of a centrifugalizing operation.

19. In a centrifugal testing separator for separating particles suspended in a liquid test sample contained in a receptacle, the combination of a vertically mounted driving shaft, a bracket substantially horizontally extending from said shaft and mounted for rotation in unison therewith, a holder adapted to receive a liquid containing receptacle, and universal joint suspension means for suspending the holder from the bracket, the said suspension means including components on the bracket and on the holder coacting one with the other and freely rotatable relative to each other about a center of rotation so as to permit the holder to occupy any position coincidental with any radius of at least a partial sphere the center of which is situated in registry with the center of rotation of the suspension means whereby the holder is capable of swinging relative to the bracket in the direction of the respective resultant of the centrifugaland inertia forces and other forces acting upon the holder and varying corresponding to the changes in the rotational speed of the driving shaft during the course of a centrifugalizing operation.

20. A testing separator as described in claim 4, wherein each of said gimbals suspension means comprise an inner and an outer gimbal ring, a pair of diametrically oppositely positioned pivots pivoting the inner ring to the outer ring, and a second pair of diametrically oppositely positioned pivots pivoting the outer ring to the bracket, the rotational axes of the pivots of said pairs of pivots crossing each other in the common center of said rings.

21. A testing separator as described in claim 4, wherein each of said gimbals suspension means comprise an inner and. an outer gimbal ring, a pair of diametrically oppositely positioned pivots pivoting the inner ring to the outer ring, and a second pair of diametrically oppositely posi- 10 tioned pivots pivoting the outer ring to the bracket, the pivots of onepair of pivots being disposed in alignment on a radial line extending from the rotational axis of the driving shaft,

5 and the pivots of the other pair of pivots being disposed in a line transversely to said radial line, the said two lines crossing each other in the center axis of said rings.

KARL OSKAR LENNART SILVERSTOLPE.

10 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 444,162 Sebenius Jan. 6, 4891 660,746 Bausch et al. Oct. 30, 1900 986,130 Binford Mar. '7, 1911 20 1,839,944 Barthels Jan. 5, 1932 2,110,308 Nelson -1 Mar. 8, 1938 2,202,157 Levy May 28, 1940 FOREIGN PATENTS 25 Number Country Date 43,103 Germany May 5, 1888 643,836 Germany Apr. 1'7, 1937 102,783 Sweden Oct. 14, 1941 

